One type of spray apparatus has traditionally been used that operates by spraying the contents of a gas container, such as a medical agent, with the help of high-pressure gas loaded in the container together with the contents. In such spray apparatuses, the gas is sprayed through a gas spray valve secured to an opening portion of the gas container. These spray apparatuses use certain types of chlorofluorocarbons as the propellant. In view of recent concerns about environmental protection, however, newly developed spray apparatuses that make use of HFC-134a, an alternative to chlorofluorocarbon, are becoming increasingly common in the marketplace.
Although HFC-134a has substantially no effects on the ozone layer, it has a significant impact on the global warming, 1000 times more significant than the impact of CO2, or even worse. Therefore, a future increase in the use of HFC-134a is expected to pose a new problem. For this reason, it is proposed to use other propellants for spray apparatuses that have less effects on the ozone layer destruction or global warming, including carbon dioxide, gaseous nitrogen, and inert gases such as helium, neon, krypton, xenon, and radon.
It is desired that these gases, as with the hydrofluorocarbons currently in use, be liquefied when used as a propellant for use in spray apparatuses in order to make the gas container small. For example, liquid carbon dioxide has a vapor pressure of 60 kgf/cm2 at 20° C. It is also preferred in terms of volume efficiency that the inert gases also be highly pressurized or liquefied and thus be put under a pressure of 50 kgf/cm2 or greater.
Handling such high-pressure gases requires a specially designed gas spray valve, such as the one described in Japanese Patent Laid-Open Publication No. Hei 8-141450.
As shown in FIG. 7, this gas spray valve includes a valve case 2 secured to an opening portion 1a of a gas container 1 and a valve pin 3 slidably received in the valve case 2. A first seal ring 4 and a second seal ring 5 are arranged within the valve case 2 and are axially spaced apart from each other. A metering chamber 6 is formed between the seal rings 4 and 5 for trapping a predetermined amount of the gas prior to spraying. The valve pin 3 includes on the lower end thereof a first valve portion 7 that comes into close contact with the first seal ring 4 when the valve pin 3 is pushed in from the outside. The valve pin 3 also includes on the upper end thereof a second valve portion 8. The second valve portion 8 consists of a large portion 8a that comes into close contact with the second seal ring 5 when the valve pin 3 is in its upper position and a small portion 8b that defines a gap together with the second seal ring 5 when the valve pin 3 has been pushed in from the outside. The metering chamber accommodates a spring 9, which always urges the valve pin 3 upward.
When the gas spray valve constructed in the above-described manner is in its steady state without the valve pin 3 being pushed from the outside, the first valve portion 7 is apart from the first seal ring 4 with the large portion 8a of the second valve portion 8 remaining in close contact with the second seal ring 5, such that the interior of the gas container 1 remains in communication with the metering chamber 6. As the valve pin 3 is pushed in from the outside, the first valve portion 7 comes into close contact with the first seal ring 4, followed by formation of a gap between the small portion 8b of the second valve portion 8 and the second seal ring 5. The gap allows the contents of the gas container 1 to pass through along with the gas. The contents and the gas are then sprayed out from the gas container 1. Since formation of the gap between the second valve portion 8 and the second seal ring 5 is immediately preceded by the first valve portion 7 coming into close contact with the first seal ring 4 to close communication between the metering chamber 6 and the interior of the gas chamber 1, a predetermined amount of the mixture of the gas and the contents trapped in the metering chamber 6 is sprayed from the gas spray valve.
A construction of gas spray valve that permits reuse of the gas container and the gas spray valve is described in Japanese Patent Laid-Open Publication No. Hei 11-301759. As shown in FIG. 8, the gas spray valve 10 includes a valve case 12 secured to an opening portion 11a of a gas container 11 and a valve pin 13 slidably received in the valve case 12. Arranged within the valve case 12 are a first seal ring 18, which comes into close contact with the outer surface of the valve pin 13 at a first position relatively close to the center of the gas container 11, and a second seal ring 19, which comes into close contact with the outer surface of the valve pin 13 at a second position relatively far from the center of the gas container 11. A metering chamber 21 is defined within the valve case 12 between the first seal ring 18 and the second seal ring 19 for trapping a predetermined amount of gas prior to spraying. The valve pin 13 includes a gas conduit 22, which extends through the valve pin 13 from the top end thereof positioned outside the gas container 11 and opens in the outer periphery of the valve pin 13 at a position axially apart from the top end. The opening of the gas conduit 22 on the outer periphery of the valve pin 13 is arranged such that it is positioned above the second seal ring 19 when the valve pin 13 is in its raised position and it is positioned below the second seal ring 19 within the metering chamber 21 when the valve pin 13 is pushed down to a first stop position or further to a second stop position at which the valve pin stops during its two-step action. The valve pin 13 further includes a first bypass portion and a second bypass portion that, together with the inner surface of the first seal ring 18, form a gap when the valve pin 13 is in the raised position and in the second stop position, respectively, so that the interior of the gas container 11 communicates with the metering chamber 21 through this gap.
When the valve pin 13 is in the raised position in the gas spray valve of the above-described construction, the opening of the gas conduit 22 on the outer periphery of the valve pin 13 is positioned above the second seal ring 19. As a result, communication between the gas conduit 22 and the metering chamber 21 is closed, whereas the metering chamber 21 remains in communication with the interior of the gas container 11 through the first bypass portion of the valve pin 13. When the valve pin 13 is pushed into the first stop position, the first seal ring 18 closes communication between the gas container 11 and the metering chamber 21, and the opening of the gas conduit 22 on the outer periphery of the valve pin 13 is positioned within the metering chamber 21. As a result, the predetermined amount of the gas trapped in the metering chamber 21 is sprayed out from the gas container 11 through the gas conduit 22. When it is desired to injector refill the gas into the gas container 11, a gas injector is connected to the valve pin 13 and the valve pin 13 is pushed into the second stop position. This causes the opening of the gas conduit 22 on the outer periphery of the valve pin 13 to move into the metering chamber 21 and brings the metering chamber 21 into communication with the interior of the gas container 11 through the second bypass portion of the valve pin 13. As a result, the gas is injected from the gas injector, through the metering chamber 21 and the second bypass portion, into the gas container 11.
When a high-pressure gas such as liquid carbon dioxide is used as a propellant for the spray apparatus, the gas container and the gas spray valve must be of considerable strength to ensure safety. To this end, more materials need to be used to construct the gas container and the gas spray valve as compared to the conventional spray apparatus, which utilizes chlorofluorocarbon propellant. Accordingly, it is not desirable, in view of efficient use of resources, to make the spray apparatus disposable, which is the case with conventional spray apparatuses. Nevertheless, the above-mentioned gas spray apparatus described in Japanese Patent Laid-Open Publication No. Hei 8-141450 does not incorporate any structure that permits recharging of the gas container with the gas and contents, and therefore, the gas containers and the gas spray valves of these gas spray apparatuses must be discarded after use.
Accordingly, it is an objective of the present invention to provide a novel gas spray valve, which is not only simpler, stronger and more durable than conventional spray valves, but also has a structure suitable for industrial production while permitting recharging of the gas container after use, and thus, efficient use of natural resources, without leading to increased production costs. It is another objective of the present invention to provide an injection adapter for use with the gas spray valve that facilitates recharging of the gas.
In general, the nozzle of the gas spray valve must be pushed into when acted upon by a force of 3 kgf or less so that the gas spray valve can be manipulated with hands and fingers. When a high-pressure gas such as liquid carbon dioxide is used as a propellant for the spray apparatus, the magnitude of the force required to push the nozzle is proportional to the cross-sectional area of the valve pin upon which the pressure of the high-pressure gas is exerted. For this reason, the diameter of the valve pin is preferably Φ2.5 or less when liquid carbon dioxide propellant is used. Although valve pins with a larger diameter may be used by employing a spring or the like to reduce the force required to push the nozzle, the use of a spring makes the structure of the spray valve complex and leads to increased production costs.
With the diameter of Φ2.5 or less, the valve pin as disclosed in Japanese Patent Laid-Open Publication No. Hei 11-301759 may become susceptible to bending or breaking when subjected to a larger force due to its reduced strength and rigidity, which results from the v-shaped groove formed to serve as a bypass for allowing the gas into the metering chamber or for permitting recharging of the gas container with the gas and desired contents. This can lead to faulty operation or malfunction of the spray apparatus.
In addition to the gas conduit for allowing the gas and the contents to be sprayed out, the valve pin includes the two V-shaped grooves. Working such a valve pin involves complicated processes that require use of various tools.
Furthermore, the gas spray valve includes in the portion to receive the valve pin two grooves to receive respective seal rings and another groove to serve as the metering chamber. Since the valve pin has a diameter of Φ2.5 or less as described above, the size of the bore for receiving the valve pin is correspondingly small. In practice, it is difficult to form the grooves through the relatively small bore. For this reason, the structure of the gas spray valve is not suitable for industrial production.